The UK's most complete GLP-1 guide
Every Question Answered. Every Side Effect Explained.
- How GLP-1 medications work
- Mounjaro vs Wegovy compared
- Injection instructions
- Side effects & solutions
- What to eat on treatment
- FAQs answered
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Thyroid Diet Plan for Weight Loss
A thyroid condition can significantly affect your weight and ability to lose weight, even with dietary changes. If you have an underactive thyroid (hypothyroidism), your metabolism slows, making weight loss more challenging. This guide explains how thyroid function influences your weight, what a thyroid-supportive diet looks like, and when to seek professional help. For personalised weight management advice, always consult your GP — especially if you suspect a thyroid problem. You can use our free BMI calculator to track where your current weight sits against NHS guidelines, and our weight converter to monitor progress across different measurements (stone, kg, or pounds).
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Calculate Your BMI Instantly
Enter your height and weight below. Supports both imperial (stone & lbs) and metric (kg). Results include NHS category, healthy weight range, and ethnicity adjustments.
What Is BMI and Why Does It Matter?
Body Mass Index (BMI) is the most widely used screening tool for assessing whether your weight falls within a healthy range. Used by the NHS, GPs, and weight management services across the UK, BMI provides a quick snapshot of your weight relative to your height. The formula is simple: your weight in kilograms divided by your height in metres squared (kg/m²).
While BMI isn't a perfect measure — it doesn't account for muscle mass, bone density, or fat distribution — it remains the standard first step in identifying potential weight-related health risks including type 2 diabetes, cardiovascular disease, high blood pressure, and certain cancers.
The NHS also recommends adjusted thresholds for people of South Asian, Chinese, or Black African heritage — a BMI of 23 or above is classified as overweight, and 27.5 as obese. Our calculator includes this adjustment as a one-click toggle.
How Thyroid Function Affects Weight Loss
Your thyroid is a gland that produces hormones controlling your metabolic rate — how many calories your body burns at rest. When your thyroid underproduces hormones (hypothyroidism), your metabolism slows, making weight loss harder even with a calorie deficit. Common thyroid conditions affecting weight include:
- Hypothyroidism — underactive thyroid, slower metabolism, weight gain or difficulty losing weight
- Hyperthyroidism — overactive thyroid, faster metabolism, weight loss (but medically concerning)
- Hashimoto's thyroiditis — autoimmune thyroid condition, often causes hypothyroidism and weight struggles
If you suspect a thyroid problem, ask your GP for a thyroid function test (TSH and free T4). Once diagnosed and properly medicated (usually levothyroxine for hypothyroidism), weight loss becomes more achievable. However, medication alone doesn't studied results — dietary and lifestyle changes remain essential. Many people with well-controlled thyroid conditions still need to lose weight through NHS weight loss strategies and calorie management to reach a healthy BMI.
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How It Works
Three simple steps to understand your weight and take action.
Enter your height and weight in our free calculator. Get your BMI, NHS category, healthy weight range, and ethnicity-adjusted thresholds instantly.
If your BMI suggests you're overweight or obese, explore our GLP-1 calculators to project potential weight loss on Mounjaro or Wegovy.
Use our progress tracker to log your weight weekly, visualise your journey with charts, and stay motivated — all stored privately in your browser.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Thyroid-Supportive Diet for Weight Loss
A thyroid-supportive diet focuses on nutrients that help thyroid function and sustainable weight loss. Key dietary principles include:
- Adequate protein: Supports muscle retention and satiety during weight loss
- Selenium and iodine: Essential minerals for thyroid hormone production (found in fish, eggs, nuts, seaweed)
- Iron and zinc: Support thyroid hormone absorption (red meat, legumes, seeds)
- Whole foods over processed: Reduces inflammation, supports energy and metabolism
- Consistent meal timing: Helps regulate blood sugar and appetite hormones
Combine a thyroid-supportive diet with a moderate calorie deficit (500 kcal/day = ~0.5 kg/week loss) and regular physical activity. If weight loss remains difficult despite proper thyroid medication and dietary effort, your GP can discuss prescription weight loss options or refer you to a specialist weight management service through the NHS.
- Dual GIP/GLP-1 receptor agonist
- Up to 22.5% body weight loss (SURMOUNT-1)
- Weekly injection, dose escalation over 20+ weeks
- Available via private prescription in the UK
- Doses: 2.5mg → 5mg → 7.5mg → 10mg → 12.5mg → 15mg
- GLP-1 receptor agonist
- Up to 15–17% body weight loss (STEP trials)
- Weekly injection, 5-step dose escalation
- NHS & private prescription available
- Doses: 0.25mg → 0.5mg → 1mg → 1.7mg → 2.4mg
Mounjaro vs Wegovy: Head-to-Head
A side-by-side comparison of the two most popular GLP-1 weight loss medications available in the UK.
| Feature | Mounjaro | Wegovy |
|---|---|---|
| Drug class | Dual GIP/GLP-1 agonist | GLP-1 agonist |
| Active ingredient | Tirzepatide | Semaglutide |
| Avg. weight loss | 15–22.5% | 12–17% |
| Key trial | SURMOUNT-1 (2022) | STEP 1 (2021) |
| Max dose | 15 mg weekly | 2.4 mg weekly |
| Escalation period | 20–32 weeks | 16–20 weeks |
| Administration | Weekly injection (pen) | Weekly injection (pen) |
| NHS availability | Private prescription only | NHS & private |
| Approx. private cost | £150–£250/month | £150–£300/month |
| Common side effects | Nausea, diarrhoea, constipation | Nausea, vomiting, diarrhoea |
Data sourced from SURMOUNT-1 and STEP 1 clinical trials. Costs are approximate and vary by provider. Always consult a prescriber.
Am I Eligible for Weight Loss Medication?
In the UK, eligibility for GLP-1 weight loss medications like Mounjaro and Wegovy is based on your BMI and overall health profile.
- BMI of 30 or above (obese)
- Age 18 or over
- No contraindicated conditions
- Committed to lifestyle changes
- BMI of 27 or above
- Plus type 2 diabetes
- Or high blood pressure
- Or obstructive sleep apnoea
Use our BMI calculator to check whether your BMI falls within the eligible range.
How We Built These Tools
Every calculator and guide on myweightcheck is built with accuracy and transparency in mind. Our BMI calculator uses the standard WHO formula with NHS-aligned category thresholds. Our GLP-1 projections are modelled on published clinical trial data from SURMOUNT and STEP studies.
All data stays on your device. We don't require sign-ups, and we don't store your health information on any server. Your progress tracker saves data locally in your browser using localStorage, so only you can see it.
We're based in the UK and our tools are designed specifically for UK users — supporting stone & lbs by default, referencing NHS guidelines, using NICE-approved medication data, and linking to GPhC-registered pharmacies.
Frequently Asked Questions
Common questions about BMI, weight loss medications, and our free UK tools.
Can thyroid problems prevent weight loss even with a healthy diet?
Yes. An underactive thyroid (hypothyroidism) significantly slows metabolism, making weight loss harder despite calorie deficit. Once properly medicated with levothyroxine and thyroid function is stable, weight loss becomes more achievable. If you're struggling to lose weight, ask your GP for a thyroid function test to rule out thyroid disease.
What foods should I eat with a thyroid condition to support weight loss?
Focus on protein-rich foods (chicken, fish, eggs), selenium sources (Brazil nuts, fish), iodine sources (seaweed, dairy), iron (lean meat, lentils), and zinc (seeds, shellfish). Choose whole foods over processed options. Combine with a calorie deficit and regular activity for sustainable weight loss.
How long does it take to lose weight after starting thyroid medication?
Weight loss typically becomes noticeable 6–8 weeks after starting levothyroxine, as thyroid hormone levels stabilise. Results vary. Your GP will monitor your TSH levels to ensure the correct dose. Even with proper medication, you'll still need a calorie deficit and lifestyle changes to lose weight consistently.
Should I try GLP-1 weight loss injections if I have a thyroid condition?
GLP-1 medications like Wegovy may be considered if you have a BMI of 30+ or 27+ with weight-related health conditions. However, eligibility and safety depend on your individual thyroid status and medications. Always discuss this with your GP or a specialist weight management service — they'll assess whether it's appropriate for you.
What's the difference between thyroid problems and needing weight loss medication?
Thyroid problems affect metabolism; weight loss medications address appetite and food cravings. Both can cause weight gain or difficulty losing weight, but for different reasons. Your GP can test your thyroid and assess whether prescription weight loss treatment (like GLP-1 medication) is suitable alongside proper thyroid management.
Ready to take control of your weight loss journey?
Start with a free BMI check, explore your GLP-1 options, or begin tracking your progress today. No sign-up. No cost. Just results.